Just about the time when you get you best practices written in stone the manufactures decides to change their philosophy. Recently I gathered manufacture recommendations on all the motors in our facility. I was using this information to build equipment specific procedures. Then Katrina hits and washes away all of our motors. So, I've start from scratch gathering equipment specific information. I have begun to notice the manufactures recommendation on the new motors do not agree with pre-existing recommendations from the same manufacture on the same motor designs. One might say "grease while running" where the other says "only while equipment is down" in big bold print. One document might say to add X amount of grease at X interval while the new document says to purge the cavity. I have seen this topic several times before be a source of confusion for many. Now it seems as though the manufacture can make up their minds either.

Waylon:

Which manufacturers state to grease while running and/or purge the bearings? Are these instructions in the operator/user manual or were they presented by the sales group?

The proper method for greasing bearings is while the motor is not operating and in specific amounts. There are physical reasons for this including bearing damage due to the hydraulic pressures that occur.

Go to http://www.reliabilityweb.com under the motors section and you will find several articles on motor greasing that I had put together at the request of Terry O'Hanlon.

Howard

I think Howard has some great ideas on greasing. We follow practices roughly the same as what he advocates (based on EPRI recommendations).

Just to play devil's advocate.

I'm not sure it's fair to say there is "one" proper method of greasing for all motors. It has always been a controversial subject. There certainly have been people who have recommended greasing while running since it results in better movement of grease within the bearing. As was mentioned somewhere along the line, manufacturer's will be reluctant to put that in writing in their instructions for fear of bearing held libel if someone injures themselves while greasing. And there is a legitimate safety question of getting to the drain port of the inboard bearing. Some motors are easier to get to than others.

Also the possibility of pumping action which can push the grease along the shaft. To play devil's advocate on that last point - that pumping action will happen when you turn the motor back on, won't it? So it's just a matter of degrees. There is more opportunity for pumping action if you lub while running but still some even if you lub while shutdown.

So to make it more complicated, if you run 24x7 for 10 months or more and no reduce in operation and no full secondary spare to change with, how would you grease the motor? In this case a +800kW feed pump motor for a wood chip fired heat plant, alternative is a expensive gasturbine, don´t think they even considered swapping just for greasing. It´s not recommended but exist. Olov

I agree Howard has put together much information on the topic. There are several informative posts here on the subject both by Howard and others. However, one can get lost in mass confusion especially when the issue is compound by the manufactures.
My goal was to take a closer look at all the recommendation at to develop a plan for sight specific implementation. However, trying to find the common denominator between methods has been somewhat elusive. The problem is that there are three major concerns to compare.
1.Service conditions
2.Frequency of Lubrication
3.Volume

Now take into consideration each manufacture adds own twist to the methods.
One company might use horse power while another might use frame size. Don't forget to add speed as another variable. The reputable papers on the subject also take different approaches. Add bearing manufactures recommendation and the possibilities are almost endless. Whether it is be bore diameter, shaft size, or something else each uses a slightly different metering stick. Often shaft size, bearing bore, speed and horse power can vary with motors of the same frame design.
Okay, now try loading all of the different approaches on one spread sheet, recalculate the variables to match and see if you can get a common answer. You probably will not get the numbers to match, but if you find the missing link please pass that information on to me. At first I assumed the answers were common. I figured the manufactures and paper writers just adjusted their methods to say they had an idea or approach they could call their own. However, I find that the gray area is significant in many cases.
In the end I guess the common sense approach is about as good as you are going to get. Getting someone, such as the in house lubrication person, to take time to cross reference motor frame, shaft dia., speed and HP power would in many cases be a monumental accomplishment. Taking that into consideration it isn't hard to see how a simple purge philosophy appears to gain merit. My goal was to provide the mechanics a single method, with one volume for each motor, at a fix interval. I realize this sounds like overkill and in some cases I tend to agree. However, if you are required to do the job right and the equipment is critical there is the reason for equipment specific practices and procedures.

One last note:
Each of my new motor suppliers recommendation are to purge or add the recommended amount of grease until new lubricate appears at the drain or shaft seal. However, in the past the recommendation was to grease on the run where now each says the motor should be down.

You mention purge philosophy and adding until grease comes out, which I assume are the same thing.

I would urge against this for the simple reason that it is not necessary and will unnecessarily overlubricate the bearing.

You can get all the info you mentioned from a walkdown of the motor nameplate which includes speed, horsepower and frame (if you need it). Also the shaft diameter can be determined direct from the bearing AFBMA number which is on the nameplate. For example 65BC03 has 65mm bearing bore which of course is mounted on a portion of the shaft which is 65mm.

To uncomplicate the issue, one thing to do is pick a set of guidelines and stick with it (rather than varying by manufacturer). I think Howard has some good guidelines. We use the EPRI guidelines which are completely described here:
http://www.machinerylubrication.com/article_detail.asp?...okgroup=Lubrication2

If you compare to guidelines like SKF, you will see the EPRI guide adds more grease quantity less frequently. I think they are pushing the envelope on reducing regreasing effort by adding less frequently and they add a little more quantity each time to try to compensate. It's probably not as ideal for the machinery reliability as a bearing manufacturer's more frequent lower quantity grease schedule, but everything's a tradeoff....the savings in regreasing time is significant if I can use an EPRI interval which might be about double the SKF interval.

Also I tend to specify a little bit more than listed for vertical motors since the guide doesn't distinguish horizontal/vertical whereas most guides will add more to vertical.

quote:

Originally posted by MotorDoc:
Waylon:

Which manufacturers state to grease while running and/or purge the bearings? Are these instructions in the operator/user manual or were they presented by the sales group?

Try SKF 'Y' Type, as one example...

As several have mentioned, this issue has been ongoing for a long time. Does anyone know of any comprehensive research that has been done related to this issue?

...'Y' Type obviously not for motors, but one case that is recommended to have, as SKF says, 'rotating' while applying grease...sorry if I threw anyone off topic here...

Link to SKF info: SKF 'Y' Type Relube info

This message has been edited. Last edited by: Jamie Dugan,

Beside the confusion on whether or not it is proper to lubricate while motor is running vs. still, there are two simple questions at least I'm struggling with.

1. Service conditions... Noria, FAG and other recommend doubling the frequency of re-greasing if operating temperature is above 150F.
This sounds reasonable as grease degrades and escapes from the cavity faster at higher temperatures.

But what about operation in a dusty environment?
In this case they still recommend frequency increase by factor of two!?!? Probably, in order to expell particle contaminated grease at a faster rate. That also sounds reasonable. But what about quantity???

They don't recommend lowering the amount also by factor of two... If this is correct, the cavity will be soon filled up to 100%, and after that adding more grease will resemble purging, which most of the people regard as a bad idea.

2. Why motor bearings require special treatment (in comparison with pillow block bearings) as far as re-greasing is concern? (Is it operating temperature?). If I'm not mistaken, SKF, FAG, etc. don't take this into account when calculating frequency and amount of re-greasing (re-plenishing).

We had an interesting application of this come up a couple weeks ago while taking acceptance measurements on an overhauled pump.

This was a large sewage pump that had been removed, reworked at a service center and returned. Apparently in an effort to save some money, the pump bearings were not touched during this process.

The pump could be freely turned by hand before running, but couldn't be turned by hand after running. OVerall readings showed a lot of high frequency noise on the pump bearings and spectral data showed a couple possible bearing tones.

Not knowing exactly what had been done to the bearings, my first thought was a bearing lubrication problem. Inspection showed grease at the bearing inlet and outlet. A few pumps from the first greasegun that could be found were added to the pump. The manufacturer's rep was concerned about overgreasing, so little grease was added.

Running the pump again showed the same possible bearing symptoms.

Concerns:
1. Are the bearings adequately greased?
2. Was the added grease a compatible type?
3. What is the condition of the grease in the bearing cavity?


How does one "ensure adequate lubrication" when the grease cavity can't be seen? Pumping in additional grease and seeing grease come out the outlet doesn't really say much for the condition of the grease.

Aside from convincing people not to try and save a buck during overhaul, any suggestions how to deal with a situation like this?

Jon
http://www.spintelligentlabs.com

Dear Members,
Lubrication philosophy never changes. The equipment is assembled with the "proper" lubrication. Once you place the equipment into use, you are also using the lubricant. Ideally, you would like to break the usage down into the smallest time interval, and "constantly" reapply lubricant to "maintain" the original "proper" amount. However; this ideal is not feasible. So we look to how close we can achieve re-lubrication. Simple PM scheduling with purge techniques will suffice in some environments, but for those requiring more exacting measures, here is my recommendation.
Use a Single Point Mechanical Grease Lubricator, battery operated, with a logic circuit to dictate how long the cartridge volume will last (based on PM). Use a Control wire to lubricate ONLY when the bearings are static (this may require a relay). This solution will give a small amount of grease, more often, when the drive is innactive. This DOES NOT replace the need for inspection! Maintenance personnel will now have more time to do actual analysis and investigate the proper lube levels. Once established, the time and cost associated with repair and maintenance should counter the cost of the single point lubricators. Based on tradition feedback, we have seen returns in as little as 6 mo., but more likely 12 to 18 months.

Jamie Dugan,
Are these instructions in the operator/user manual or were they presented by the sales group?

The new motors came with instruction listed as Installation and Maintenance Instructions.
We're in a hurry to replace piles of motors so the specification requirements have most likely been a secondary issue.

Examples straight from the manuals -

Old information:
Anti-friction bearings may be lubricated with the motor running or stationary

New information:
Bearings should be lubricated while stationary and the motor is warm.

Contradictory information:
It is advisable to re-grease when the motor is running to allow the new grease to be evenly distributed inside the bearing

Waylon,

The info is from the SKF Interactive Engineering Catalog website. However the info is also included with the packaging of the 'Y' type bearings.

Just to reiterate, 'y' types are not found in motors. I was off topic here...

SKF IEC